Epoxidized polyisoprene tire tread

Abstract

The present invention relates to a tire tread comprising a rubber composition which improves the compromise between wear and durability of the tire, especially a tire intended to run off-road. The composition comprises: from more than 50 to 100 phr of a polyisoprene matrix, the polyisoprene matrix containing an epoxidized polyisoprene having a molar degree of epoxidation ranging from 5% to less than 50%, a carbon black and a silica, the weight of carbon black being greater than 50% of the total weight of carbon black and silica, from 0 to less than 2 phr of a coupling agent, and a crosslinking system. The epoxidized polyisoprene is an epoxidized natural rubber or an epoxidized synthetic polyisoprene having a molar content of 1,4-cis bonds of at least 90% before epoxidation, or a mixture thereof, and, if the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 25%, the rubber composition contains more than 50 phr of epoxidized polyisoprene.

1 .- 28 . (canceled) 
     
     
         29 . A tire tread comprising a rubber composition comprising:
 from more than 50 to 100 phr of a polyisoprene matrix, the polyisoprene matrix containing an epoxidized polyisoprene having a molar degree of epoxidation ranging from 5% to less than 50%;   a carbon black and a silica, the weight of carbon black being greater than 50% of the total weight of carbon black and silica;   from 0 to less than 2 phr of a coupling agent; and   a crosslinking system,   wherein the epoxidized polyisoprene is an epoxidized natural rubber or an epoxidized synthetic polyisoprene having a molar content of 1,4-cis bonds of at least 90% before epoxidation, or a mixture thereof, and   wherein, if the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 25%, the rubber composition contains more than 50 phr of epoxidized polyisoprene.   
     
     
         30 . The tire tread according to  claim 29 , wherein the content of the coupling agent is from 0 to less than 1 phr. 
     
     
         31 . The tire tread according to  claim 30 , wherein the content of the coupling agent is from 0 to less than 0.5 phr. 
     
     
         32 . The tire tread according to  claim 31 , wherein the content of the coupling agent is equal to 0 phr. 
     
     
         33 . The tire tread according to  claim 29 , wherein the content of carbon black is from 30 to 90 phr. 
     
     
         34 . The tire tread according to  claim 33 , wherein the content of carbon black is from 30 to 70 phr. 
     
     
         35 . The tire tread according to  claim 34 , wherein the content of carbon black is from 35 to 60 phr. 
     
     
         36 . The tire tread according to  claim 29 , wherein the content of silica is greater than 0 phr and less than or equal to 35 phr. 
     
     
         37 . The tire tread according to  claim 36 , wherein the content of silica is from 2 to 35 phr. 
     
     
         38 . The tire tread according to  claim 29 , wherein the carbon black has a BET specific surface area of at least 90 m 2 /g. 
     
     
         39 . The tire tread according to  claim 38 , wherein the carbon black has a BET specific surface area of at least 100 m 2 /g. 
     
     
         40 . The tire tread according to  claim 29 , wherein the composition comprises a covering agent for the silica. 
     
     
         41 . The tire tread according to  claim 40 , wherein the covering agent is a polyethylene glycol. 
     
     
         42 . The tire tread according to  claim 29 , wherein the crosslinking system is a vulcanization system. 
     
     
         43 . The tire tread according to  claim 29 , wherein the epoxidized polyisoprene is an epoxidized natural rubber. 
     
     
         44 . The tire tread according to  claim 29 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 35%. 
     
     
         45 . The tire tread according to  claim 44 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 30%. 
     
     
         46 . The tire tread according to  claim 45 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 25%. 
     
     
         47 . The tire tread according to  claim 29 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 40%. 
     
     
         48 . The tire tread according to  claim 47 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 10% to 35%. 
     
     
         49 . The tire tread according to  claim 29 , wherein the content of the polyisoprene matrix is greater than 80 phr. 
     
     
         50 . The tire tread according to  claim 29 , wherein the content of epoxidized polyisoprene is greater than 80 phr. 
     
     
         51 . The tire tread according to  claim 50 , wherein the content of epoxidized polyisoprene is equal to 100 phr. 
     
     
         52 . The tire tread according to  claim 29 , wherein the polyisoprene matrix contains a polyisoprene having a molar content of 1,4-cis bonds of at least 90%. 
     
     
         53 . The tire tread according to  claim 52 , wherein the polyisoprene matrix is a mixture of the polyisoprene having a molar content of 1,4-cis bonds of at least 90% and the epoxidized polyisoprene. 
     
     
         54 . The tire tread according to  claim 52 , wherein the polyisoprene having a molar content of 1,4-cis bonds of at least 90% is natural rubber. 
     
     
         55 . The tire tread according to  claim 29  further comprising another diene elastomer. 
     
     
         56 . The tire tread according to  claim 55 , wherein the another diene elastomer is an essentially unsaturated diene elastomer selected from the group consisting of polybutadienes, butadiene copolymers, isoprene copolymers and mixtures thereof. 
     
     
         57 . The tire tread according to  claim 29 , wherein the content of the polyisoprene matrix is equal to 100 phr. 
     
     
         58 . A process for preparing the tire tread according to  claim 29  comprising the steps of:
 adding the carbon black, the silica and, if present, the coupling agent to the polyisoprene matrix during a first non-productive step by kneading thermomechanically until a maximum temperature of between 110° C. and 200° C. is reached; 
 cooling the mixture to a temperature of less than 110° C.; 
 subsequently incorporating the crosslinking system; 
 kneading the mixture up to a maximum temperature of less than 110° C. in order to obtain the rubber composition; and 
 calendaring or extruding the rubber composition into the tire tread. 
 
     
     
         59 . A tire comprising a tire tread according to  claim 29 . 
     
     
         60 . The tire according to  claim 59 , wherein the tire is intended to bear heavy loads. 
     
     
         61 . The tire according to  claim 60 , wherein the tire is intended to runoff-road. 
     
     
         62 . The tire according to  claim 61 , wherein the tire is a tire for a civil engineering vehicle. 
     
     
         63 . A process for preparing the tire according to  claim 59  comprising the steps of:
 adding the carbon black, the silica and, if present, the coupling agent to the polyisoprene matrix during a first non-productive step by kneading thermomechanically until a maximum temperature of between 110° C. and 200° C. is reached; 
 cooling the mixture to a temperature of less than 110° C.; 
 subsequently incorporating the crosslinking system; 
 kneading up to a maximum temperature of less than 110° C. in order to obtain the rubber composition; and 
 calendering or extruding the rubber composition into the tire tread.